Using LVDS

Thanks Frank! To test out the connection, I simplified my design.

Example:

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Board 1 and 2:

input RECEIVING;

output SENDING;

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I am assigning only the (p) pins in the qsf file, because I read that the (n) pins are automatically assigned by the fitter.

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Board 1:

set_location_assignment PIN_AC25 -to SENDING

set_instance_assignment -name IO_STANDARD LVDS -to SENDING

set_location_assignment PIN_AL32 -to RECEIVING

set_instance_assignment -name IO_STANDARD LVDS -to RECEIVING

Board 2:

set_location_assignment PIN_AC25 -to SENDING

set_instance_assignment -name IO_STANDARD LVDS -to SENDING

set_location_assignment PIN_AL32 -to RECEIVING

set_instance_assignment -name IO_STANDARD LVDS -to RECEIVING

--- Quote End ---

I am not using any megafunction, just using assign statements in Verilog. But I do not see the right result on SignalTap. "Receiving" which is an input to both boards (and an output from the other) is constantly high on both boards.

Can you please suggest what I may be doing wrong?